On Thu, Sep 23, 2021 at 07:19:41PM -0700, Andrew Morton wrote:

On Thu, 23 Sep 2021 19:25:12 -0400 Peter Xu [off-list ref] wrote:

quoted

In RHEL's gating selftests we've encountered memory corruption in the uffd
event test even with upstream kernel:

...


We can mark the Fixes tag upon 0db282ba2c12 as it's reported to only happen
there, however the real "Fixes" IMHO should be 8ba6e8640844, as before that
commit we'll always do explicit release_pages() before registration of uffd,
and 8ba6e8640844 changed that logic by adding extra unmap/map and we didn't
release the pages at the right place.  Meanwhile I don't have a solid glue
anyway on whether posix_memalign() could always avoid triggering this bug,
hence it's safer to attach this fix to commit 8ba6e8640844.

Thanks.  I added a cc:stable to this.  I don't think we want selftests
in older kernels to be falsely reporting kernel bugs?

Not sure how we normally handle such case for selftests, but I agree.

Btw, 8ba6e8640844 is merged in 5.14, so the only stable branch that will need
it will be 5.14.y; it can be applied cleanly there.

Thanks,

-- 
Peter Xu